Acetylsalicylic acid provides cerebrovascular protection from oxidant damage in salt-loaded stroke-prone rats

Inflammatory processes may play a pivotal role in the pathogenesis of cerebrovascular injury in salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP). Recent reports revealed that acetylsalicylic acid (aspirin) has anti-oxidative properties and elicits nitric oxide release by a direct activation of the endothelial NO synthase. The present study was designed to determine whether low-dose aspirin might prevent cerebrovascular injury in salt-loaded SHRSP by protecting oxidative damage. Nine-week-old SHRSP were fed a 0.4% NaCl or a 4% NaCl diet with or without treatment by naproxen (20 mg/kg/day), salicylic acid (5 mg/kg/day), or aspirin (5 mg/kg/day) for 5 weeks. Blood pressure, blood brain barrier impairment, mortality, and the parameters of cerebrovascular inflammation and damage were compared among them. High salt intake in SHRSP significantly increased blood brain barrier impairment and early mortality, which were suppressed by treatment with aspirin independent of changes in blood pressure. Salt loading significantly increased superoxide production in basilar arteries of SHRSP, which were significantly suppressed by treatment with aspirin. Salt loading also significantly decreased NOS activity in the basilar arteries of SHRSP, which were significantly improved by treatment with aspirin. At 5 weeks after salt loading, macrophage accumulation and matrix metalloproteinase-9 activity at the stroke-negative area in cerebral cortex of SHRSP were significantly reduced by treatment with aspirin. These results suggest that low-dose aspirin may exert protective effects against cerebrovascular inflammation and damage by salt loading through down-regulation of superoxide production and induction of nitric oxide synthesis.     

O2-acetoxymethyl-protected diazeniumdiolate-based NSAIDs (NONO-NSAIDs): synthesis, nitric oxide release, and biological evaluation studies

A novel group of O2-acetoxymethyl-protected diazeniumdiolate-based non-steroidal anti-inflammatory prodrugs (NONO-NSAIDs) were synthesized by esterifying the carboxylate group of aspirin, ibuprofen, or indomethacin with O2-acetoxymethyl 1-[N-(2-hydroxyethyl)-N-methylamino]diazeniumdiolate. The resulting nitric oxide (*NO)-releasing prodrugs (7-9) did not exhibit in vitro cyclooxygenase (COX) inhibitory activity against the COX-1 and COX-2 isozymes (IC50s>100 microM). In contrast, prodrugs 7 and 8 significantly decreased carrageenan-induced rat paw edema showing enhanced in vivo anti-inflammatory activities (ID50's=552 and 174 micromol/kg, respectively) relative to those of the parent NSAIDs aspirin (ID50=714 micromol/kg) and ibuprofen (ID50=326 micromol/kg). The rate of porcine liver esterase-mediated *NO release from prodrugs 7-9 (2 mol of *NO/mol of test compound in 0.6-6.5 min) was substantially higher compared to that observed without enzymatic catalysis (about 1 mol of *NO/mol of test compound in 40-48 h). These incubation studies suggest that both *NO and the parent NSAID would be released upon in vivo activation (hydrolysis) by esterases. Data acquired in an in vivo ulcer index (UI) assay showed that NONO-aspirin (UI=0.8), NONO-indomethacin (UI=1.3), and particularly NONO-ibuprofen (UI=0) were significantly less ulcerogenic compared to the parent drugs aspirin (UI=57), ibuprofen (UI=46) or indomethacin (UI=34) at equimolar doses. The release of aspirin and *NO from the NONO-aspirin (7) prodrug constitutes a potentially beneficial property for the prophylactic prevention of thrombus formation and adverse cardiovascular events such as stroke and myocardial infarction.     

Blue laser light increases perfusion of a skin flap via release of nitric oxide from hemoglobin

It has recently been shown that nitrosyl complexes of hemoglobin (NO-Hb) are sensitive to low-level blue laser irradiation, suggesting that laser irradiation can facilitate the release of biologically active nitric oxide (NO), which can affect tissue perfusion. The aim of this study was to evaluate the therapeutic value of blue laser irradiation for local tissue perfusion after surgical intervention. Blood was withdrawn from a rat, exposed to NO and infused back to the same rat or used for in vitro experiments. In vitro, an increase of NO-Hb levels (electron paramagnetic resonance spectroscopy) up to 15 microM in rat blood did not result in the release of detectable amounts of NO (NO selective electrode). Blue laser irradiation of NO-Hb in blood caused decomposition of NO-Hb complexes and release of free NO. Systemic infusion of NO-Hb in rats affected neither systemic circulation (mean arterial pressure) nor local tissue perfusion (Doppler blood flow imaging system). In contrast, a clear enhancement of local tissue perfusion was observed in epigastric flap when elevated NO-Hb levels in blood were combined with local He-Cd laser irradiation focused on the left epigastric artery. The enhancement of regional tissue perfusion was not accompanied by any detectable changes in systemic circulation. This study demonstrates that blue laser irradiation improves local tissue perfusion in a controlled manner stimulating NO release from NO-Hb complexes.     

Effects of nitric oxide and prostacyclin on deformability and aggregability of red blood cells of rats ex vivo and in vitro.

Although many diseases of the heart and circulatory system have been linked with insufficient deformability and increased aggregability of red blood cells, there are only a few drugs which can modulate these biological functions of erythrocytes. Here, we show evidences that iloprost, stable prostacyclin analogue and SIN-1, active metabolite of molsidomine which spontaneously releases NO, may be sufficient pharmacological tools for modulating red blood cell deformability and aggregability. Deformability of red blood cells was measured by shear stress laser diffractometer (Rheodyn SSD) and expressed in percent of red blood cell deformability index (DI). MA-1 (Myrenne) erythrocyte aggregometer was used for photometric measurements of aggregability in arbitrary units (MEA) of mean extent of aggregation. Experiments were carried out on rats ex vivo and in vitro using whole rat blood or isolated erythrocytes. Ex vivo SIN-1 (infusion 2 mg/kg/min i.v.) and iloprost (bolus injection 10 microg/kg i.v.) significantly improved erythrocyte deformability and aggregability at 5-15 min after administration. L-NAME (10 mg/kg i.v.)- inhibitor of nitric oxide synthase, and aspirin (1 mg/kg i.v.) caused worsening of deformability of erythrocytes in experiments ex vivo. Studies in vitro also revealed improvement of red blood cell deformability and aggregability by SIN-1 (3 microM, 15 min incubation at 22 degrees C) or iloprost (1 microM, 15 min incubation at 22 degrees C) and this phenomenon appeared not only in whole blood but also in isolated red cells. It is concluded that NO- and prostacyclin-induced improvement of red blood cell deformability and aggregability results from direct action of these compounds on erythrocytes. NO-donors and iloprost could be useful in the treatment of disorders of blood fluidity.     

Synthesis and antileishmanial activity of novel buparvaquone oxime derivatives

Novel oxime derivatives (2, 3 and 5) of buparvaquone (1) and O-methyl-buparvaquone (4) were synthesized and their in vitro activities against Leishmania donovani, the causative agent of visceral leishmaniasis (VL), were determined. Buparvaquone-oxime (2) was also studied as a bioreversible prodrug structure of buparvaquone (1). Buparvaquone-oxime (2) released buparvaquone (1) in vitro when it was incubated with induced rat liver microsomes, which suggests that the oxime-structure is a useful prodrug template for developing novel prodrugs of buparvaquone and other hydroxynaphthoquinones. Moreover, the formation of NO(2)(-) , formed via oxidation of NO, was confirmed during the bioconversion. The release of NO from buparvaquone-oxime (2) may provide an additional therapeutic effect in the treatment of leishmaniasis. Buparvaquone-oxime (2) and buparvaquone-O-methyloxime (3) demonstrated moderate activity against amastigotes of the Leishmania species that causes VL. However, the studied oximes (2, 3) most probably did not release buparvaquone (1) and NO during the present in vitro experiment. Further in vivo studies are needed to verify the biological activity of buparvaquone-oximes in the treatment of leishmaniasis.     

神经系统中的一氧化氮

一氧化氮(NO)是一种广泛存在的独特的生物信使因子和效应因子.NO参与脑内许多生理功能和病理生理过程.NO调节神经递质释放和脑血流,参与神经发育和基因表达调控.NO可能作为一种逆行信使物质参与海马的长时程突触传递增强和小脑的长时程突触传递抑制.过多的NO则具有神经毒性并与许多神经系统疾病有关.     

An Intact Kidney Slice Model to Investigate Vasa Recta Properties and Function in situ

Background: Medullary blood flow is via vasa recta capillaries, which possess contractile pericytes. In vitro studies using isolated descending vasa recta show that pericytes can constrict/dilate descending vasa recta when vasoactive substances are present. We describe a live kidney slice model in which pericyte-mediated vasa recta constriction/dilation can be visualized in situ. Methods: Confocal microscopy was used to image calcein, propidium iodide and Hoechst labelling in 'live' kidney slices, to determine tubular and vascular cell viability and morphology. DIC video-imaging of live kidney slices was employed to investigate pericyte-mediated real-time changes in vasa recta diameter. Results: Pericytes were identified on vasa recta and their morphology and density were characterized in the medulla. Pericyte-mediated changes in vasa recta diameter (10-30%) were evoked in response to bath application of vasoactive agents (norepinephrine, endothelin-1, angiotensin-II and prostaglandin E(2)) or by manipulating endogenous vasoactive signalling pathways (using tyramine, L-NAME, a cyclo-oxygenase (COX-1) inhibitor indomethacin, and ATP release). Conclusions: The live kidney slice model is a valid complementary technique for investigating vasa recta function in situ and the role of pericytes as regulators of vasa recta diameter. This technique may also be useful in exploring the role of tubulovascular crosstalk in regulation of medullary blood flow.     

Nitric Oxide in Systemic and Pulmonary Hypertension

Endothelium-derived nitric oxide (NO) is an important gas molecule in the regulation of vascular tone and arterial pressure. It has been considered that endothelial dysfunction with impairment of NO production contributes to a hypertensive state. Alternatively, long-term hypertension may affect the endothelial function, depress NO production, and thereby reduce the dilator action on vasculatures. There were many studies to support that endothelium-dependent vasodilatation was impaired in animals and humans with long-term hypertension. However, results of some reports were not always consistent with this consensus. Recent experiments in our laboratory revealed that an NO synthase inhibitor, N^G-nitro-L-arginine monomethyl ester (L-NAME) caused elevation of arterial pressure (AP) in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). The magnitude of AP increase following NO blockade with L-NAME was much higher in SHR than WKY. In other experiments with the use of arterial impedance analysis, we found that L-NAME slightly or little affected the pulsatile hemodynamics including characteristic impedance, wave reflection and ventricular work. Furthermore, these changes were not different between SHR and WKY. The increase in AP and total peripheral resistance (TPR) following NO blockade in SHR were significantly greater than those in WKY, despite higher resting values of AP and TPR in SHR. In connection with the results of other studies, we propose that heterogeneity with respect to the involvement of NO (impairment, no change or enhancement) in the development of hypertension may exist among animal species, hypertensive models and different organ vessels. Our study in SHR provide evidence to indicate that the effects of basal release of NO on the arterial pressure and peripheral resistance are not impaired, but enhanced in the hypertensive state. The increase in NO production may provide a compensatory mechanism to keep the blood pressure and peripheral resistance at lower levels. The phenomenon of enhanced NO release also occurs in certain type of pulmonary hypertension. We first hypothesized that a decrease in NO formation might be responsible for the pulmonary vasoconstriction during hypoxia. With the measurement of NO release in the pulmonary vein, we found that ventilatory hypoxia produced pulmonary hypertension accompanying an increase in NO production. Addition of NO inhibitor (L-NAME), blood or RBC into the perfusate attenuated or abolished the NO release, while potentiating pulmonary vasoconstriction. During hypoxia, the increased NO formation in the pulmonary circulation similarly exerts a compensatory mechanism to offset the degree of pulmonary vasoconstriction.     

Korea red ginseng water extract increases nitric oxide concentrations in exhaled breath.

Panax ginseng is well known to enhance the release of nitric oxide (NO) from endothelial cells of the rat aorta and to reduce blood pressure in animals. In this study, we investigated the effects of water extract of Korea red ginseng (KRG) on NO concentration levels in the exhaled breath, blood pressure, and heart rate of human volunteers. We also are interested in whether NO levels in exhaled breath are increased by KRG extract, and correlated with blood pressure and heart rate. Twelve healthy, non-smoking male volunteers were recruited for this study. A single administration of KRG water extract (500 mg/50 kg) increased NO levels in exhaled breath, and concomitantly decreased mean blood pressure and heart rate. The correlation value between NO levels and heart rate (r = 0.94), and the correlation value between NO levels and heart rate (r = 0.84) are significant (P < 0.01). Linear regression analysis shows the clear conversed correlation between NO levels and blood pressure as well as heart rate. Therefore, present data suggest that KRG may be useful for the treatment of hypertension and pulmonary vascular obstruction.     

The effect of aspirin and two nitric oxide donors on the infarcted heart in situ

Nitric oxide (NO) donors are heterogeneous substances which release NO, a biologically active compound. NO released by nitric oxide donors has important effects on the circulation by causing vasodilation, diminishing myocardial contractile force, inhibiting platelet aggregation, and counteracting the effects of thromboxane A2. In the infarcted heart, activation of the inducible form of nitric oxide synthase (iNOS) and the formation of prostacyclin and thromboxane A2 by cyclooxygenase (COX) were increased. Myocardial infarction also resulted in increased myocardial NO production. Aspirin (acetylsalicylic acid. ASA) at low concentration (35 mg/kg/day) fails to change iNOS production, in contrast to higher dose (150 mg/kg/day) which, as previously shown, inhibits iNOS activity. ASA at all doses also suppresses myocardial prostanoid formation because of inhibition of COX. Recently, two NO donors have been synthesized: NCX 4016 and Diethylenetriamine/NO (DETA/NO). NCX 4016 combines an NO-releasing moiety with a carboxylic residue via an esteric bond. We describe here that NCX 4016 (65 mg/kg/day) increased prostacyclin and thromboxane A2 production in the infarcted heart muscle, overcoming the inhibitory effects of ASA. As a result of nitric oxide release, oxidation products of NO (NO2- and NO3-; NOx) in arterial blood rose following administration of NCX 4016. On oral administration, NCX 4016 did not change systemic arterial pressure. The effects of a single NO donor, DETA/NO (1.0 mg/kg/day) on the infarcted heart were also investigated On intravenous administration, the compound increased NO concentration in arterial blood slightly but to a lesser degree than NCX 4016. Like NCX 4016, it raised myocardial production of prostacyclin and thromboxane A2 in the infarcted heart. However, it caused a severe fall in blood pressure. These findings demonstrate that newly-synthesized NO donors release nitric oxide in situ and increase myocardial production of prostanoids. NCX 4016 has therapeutic potential because it can be orally administered, lacks hypotensive effects, increases blood levels of nitric oxide and myocardial prostacyclin production.     

Construction and evaluation of nitric oxide generating vascular graft material loaded with organoselenium catalyst via layer-by-layer self-assembly

A new biomimetic material for artificial blood vessel with in situ catalytic generation of nitric oxide(NO) was prepared in this study. Organoselenium immobilized polyethyleneimine as NO donor catalyst and sodium alginate were alternately loaded onto the surface of electrospun polycaprolactone matrix via electrostatic layer-by-layer self-assembly. This material revealed significant NO generation when contacting NO donor S-nitrosoglutathione(GSNO). Adhesion and spreading of smooth muscle cells were inhibited on this material in the presence of GSNO, while proliferation of endothelial cells was promoted. In vitro platelet adhesion and arteriovenous shunt experiments demonstrated good antithrombotic properties of this material, with inhibited platelet activation and aggregation, and prevention of acute thrombosis. This study may provide a new method of improving cellular function and antithrombotic property of vascular grafts.     

The haemoflagellate Trypanoplasma borreli induces the production of nitric oxide,which is associated with modulation of carp (Cyprinus carpio L.) leucocyte functions

In an attempt to characterise the role of nitric oxide (NO) in immune responses of carp, carp leucocytes obtained during an acute T. borreli infection were examined, for their capacity to generate NO. In a second set of experiments the impact NO on viability of the parasite and on the modulation of functional carp leucocyte responses were tested in vitro. Both in carp head-kidneys and in the peripheral blood, the fractions of lymphoblasts among separated leucocytes were increased. However, the relative proportions of granulocytes among head-kidney leucocytes (HKL) significantly decreased during infection, whereas granulocytes appeared among peripheral blood leucocytes (PBL). The cellular dynamics of HKL and PBL of infected carp were paralleled by an enhanced spontaneous NO release in vitro. NO production was further increased after addition of viable parasites to these cultures. The hypothesis that NO had a possible role in granulocyte activation and lymphocyte proliferation in carp was supported by the reduction of mitogen-induced proliferative responses of PBL from healthy carp in the presence of NO donor substances. The negative effects of NO on lymphocyte proliferation were contrasted by enhancing effects on granulocyte functions: the inhibition of NO generation in T. borreli-stimulated HKL cultures by the l-arginine analogue L-NMMA reduced the viability of granulocytes and their phagocytic activity. Even massive amounts of nitric oxide produced by donor substances (up to 600 micromol l(-1) NO(-)(2)) caused no reduction in the numbers of viable T. borreli flagellates in vitro. Thus, in carp, T. borreli seems to induce high amounts of NO in vivo which are apparently not harmful for the parasite but which may interfere with co-ordinated interactions of activated cells aiming at the defence of the parasite.     

New insights into nitric oxide and coronary circulation

Since its discovery over 20 years ago as an intercellular messenger, nitric oxide (NO), has been extensively studied with regard to its involvement in the control of the circulation and, more recently, in the prevention of atherosclerosis. The importance of NO in coronary blood flow control has also been recognized. NO-independent vasodilation causes increased shear stress within the blood vessel which, in turn, stimulates endothelial NO synthase activation, NO release and prolongation of vasodilation. Reactive hyperemia, myogenic vasodilation and vasodilator effects of acetylcholine and bradykinin are all mediated by NO. Ischemic preconditioning, which protects the myocardium from cellular damage and arrhythmias, is itself linked with NO and both the first and second windows of protection may be due to NO release. Exercise increases NO synthesis via increases in shear stress and pulse pressure and so it is likely that NO is an important blood flow regulatory mechanism in exercise. This phenomenon may account for the beneficial effects of exercise seen in atherosclerotic individuals. Whilst NO plays a protective role in preventing atherosclerosis via superoxide anion scavenging, risk factors such as hypercholesterolemia reduce NO release leading the way for endothelial dysfunction and atherosclerotic lesions. Exercise reverses this process by stimulating NO synthesis and release. Other factors impacting on the activity of NO include estrogens, endothelins, adrenomedullin and adenosine, the last appearing to be a compensatory pathway for coronary control in the presence of NO inhibition. These studies reinforce the pivotal role played by the substance in the control of coronary circulation.     

Protection of lung tissue against ischemia/reperfusion injury by preconditioning with inhaled nitric oxide in an in situ pig model of normothermic pulmonary ischemia

Topical administration of nitric oxide (NO) by inhalation is currently used as therapy in various pulmonary diseases, but preconditioning with NO to ameliorate lung ischemia/reperfusion (I/R) injury has not been fully evaluated. In this study, we investigated the effects of NO inhalation on functional pulmonary parameters using an in situ porcine model of normothermic pulmonary ischemia. After left lateral thoracotomy, left lung ischemia was maintained for 90 min, followed by a 5h reperfusion period (group I, n = 7). In group II (n = 6), I/R was preceded by inhalation of NO (10 min, 15 ppm). Animals in group III (n = 7) underwent sham surgery without NO inhalation or ischemia. In order to evaluate the effects of NO preconditioning, lung functional and hemodynamic parameters were measured, and the zymosan-stimulated release of reactive oxygen species in arterial blood was determined. Animals in group I developed significant pulmonary I/R injury, including pulmonary hypertension, a decreased pO(2) level in pulmonary venous blood of the ischemic lung, and a significant increase of the stimulated release of reactive oxygen species. All these effects were prevented, or the onset (release of reactive oxygen species) was delayed, by NO inhalation. These results indicate that preconditioning by NO inhalation before lung ischemia is protective against I/R injury in the porcine lung.     

Visible light-induced nitric oxide release from a novel nitrobenzene derivative cross-conjugated with a coumarin fluorophore

Nitric oxide (NO) is a well-known free-radical molecule which is endogenously biosynthesised and shows various functions in mammals. To investigate NO functions, photocontrollable NO donors, compounds which release NO in response to light, are expected to be potentially useful. However, most of the conventional NO donors require harmful ultra-violet light for NO release. In this study, two dimethylnitrobenzene derivatives conjugated with coumarins were designed, synthesized and evaluated as photocontrollable NO donors. The optical properties and efficiency of photo-induced NO release were dependent upon the nature of the conjugation system. One of these compounds, Bhc-DNB (1), showed spatiotemporally well-controlled NO release in cultured cells upon exposure to light in the less-cytotoxic visible wavelength range (400–430 nm).     

Role of nitric oxide after brain ischaemia

Ischaemic stroke is the second or third leading cause of death in developed countries. In the last two decades substantial research and efforts have been made to understand the biochemical mechanisms involved in brain damage and to develop new treatments. The evidence suggests that nitric oxide (NO) can exert both protective and deleterious effects depending on factors such as the NOS isoform and the cell type by which NO is produced or the temporal stage after the onset of the ischaemic brain injury. Immediately after brain ischaemia, NO release from eNOS is protective mainly by promoting vasodilation; however, after ischaemia develops, NO produced by overactivation of nNOS and, later, NO release by de novo expression of iNOS contribute to the brain damage. This review article summarizes experimental and clinical data supporting the dual role of NO in brain ischaemia and the mechanisms by which NO is regulated after brain ischaemia. We also review NO-based therapeutic strategies for stroke treatment, not only those directly linked with the NO pathway such as NO donors and NOS inhibitors but also those partially related like statins, aspirin or lubeluzole.     

Aspirin inhibits osteoclast formation and wear-debris-induced bone destruction by suppressing mitogen-activated protein kinases

Excessive osteoclast recruitment and activation is the chief cause of periprosthetic osteolysis and subsequent aseptic loosening, so blocking osteolysis may be useful for protecting against osteoclastic bone resorption. We studied the effect of aspirin on titanium (Ti)-particle-induced osteolysis in vivo and in vitro using male C57BL/6J mice randomized to sham (sham surgery), Ti (Ti particles), low-dose aspirin (Ti/5 mg·kg⁻¹·d⁻¹ aspirin), and high-dose aspirin (Ti/30 mg·kg⁻¹·d⁻¹ aspirin). After 2 weeks, a three-dimensional reconstruction evaluation using micro-computed tomography and histomorphology assessment were performed on murine calvariae. Murine hematopoietic macrophages and RAW264.7 lineage cells were studied to investigate osteoclast formation and function. Aspirin attenuated Ti-particle-induced bone erosion and reduced osteoclasts. In vitro, aspirin suppressed osteoclast formation, osteoclastic-related gene expression, and osteoclastic bone erosion in a dose-dependent manner. Mechanically, aspirin reduced osteoclast formation by suppressing receptor activator of nuclear factor kappa-B ligand-induced activation of extracellular signal-related kinase, p-38 mitogen-activated protein kinase, and c-Jun N-terminal kinase. Thus, aspirin may be a promising option for preventing and curing osteoclastic bone destruction, including peri-implant osteolysis.     

Prostaglandin biosynthesis does not participate in isoproterenol-induced renin release

Rat renal slices were incubated in two different media. One was a normal K, physiological saline solution and the other a high K medium. Renin release was measured every 15 min in the presence and absence of 10(-6) M isoproterenol and also in the presence and absence of aspirin, 0.8 or 1.6 X 10(-5) M. In all experiments renin release was linear during the 75 min of incubation. Isoproterenol increased renin release by approximately 100%. This was the case even in the presence of aspirin which significantly inhibited prostaglandin release (PGE2, PGF2 alpha and 6-keto-PGF1 alpha). Nor was there any reduction in the basal secretory rate by aspirin alone. These data are taken to indicate that aspirin in pharmacological doses does not interfere with either in vitro basal release rates of renin, nor the response to B agonists. It is also suggested that B agonists do not exert their effect by stimulating prostaglandin secretion.     

Nitrosyl-cobinamide, a new and direct nitric oxide releasing drug effective in vivo

A limited number of nitric oxide (NO)-generating drugs are available for clinical use for acute and chronic conditions. Most of these agents are organic nitrates, which do not directly release NO; tolerance to the drugs develops, in part, as a consequence of their conversion to NO. We synthesized nitrosyl-cobinamide (NO-Cbi) from cobinamide, a structural analog of cobalamin (vitamin B12). NO-Cbi is a direct NO-releasing agent that we found was stable in water, but under physiologic conditions, it released NO with a half-life of 30 mins to 1 h. We show in five different biological systems that NO-Cbi is an effective NO-releasing drug. First, in cultured rat vascular smooth muscle cells, NO-Cbi induced phosphorylation of vasodilator-stimulated phosphoprotein, a downstream target of cGMP and cGMP-dependent protein kinase. Second, in isolated Drosophila melanogaster Malpighian tubules, NO-Cbi-stimulated fluid secretion was similar to that stimulated by Deta-NONOate and a cGMP analog. Third, in isolated mouse hearts, NO-Cbi increased coronary flow much more potently than nitroglycerin. Fourth, in contracted mouse aortic rings, NO-Cbi induced relaxation, albeit to a lesser extent than sodium nitroprusside. Fifth, in intact mice, a single NO-Cbi injection rapidly reduced blood pressure, and blood pressure returned to normal after 45 mins; repeated NO-Cbi injections induced the expected fall in blood pressure. These studies indicate that NO-Cbi is a useful NO donor that can be used experimentally in the laboratory; moreover, it could be developed into a vasodilating drug for treating hypertension and potentially other diseases such as angina and congestive heart failure.     

Involvement of glutamate–cystine/glutamate transporter system in aspirin-induced acute gastric mucosa injury

Large-dose or long-term use of aspirin tends to cause gastric mucosa injury, which is recognized as the major side effect of aspirin. It has been demonstrated that glutamate exerts a protective effect on stomach, and the level of glutamate is critically controlled by cystine/glutamate transporter (Xc⁻). In the present study, we investigated the role of glutamate–cystine/glutamate transporter system in aspirin-induced acute gastric mucosa injury in vitro and in vivo. Results showed that in human gastric epithelial cells, aspirin incubation increased the activity of LDH and the number of apoptotic cells, meanwhile down-regulated the mRNA expression of Xc⁻ accompanied with decreased glutamate release. Similar results were seen in a rat model. In addition, exogenous l-glutamate attenuated the gastric mucosa injury and cell damage induced by aspirin both in vitro and in vivo. Taken together, our results demonstrated that acute gastric mucosa injury induced by aspirin is related to reduction of glutamate–cystine/glutamate transporter system activity.